1. Field of the Invention
The present invention relates generally to an impulse generation circuit, and more particularly to an impulse generation circuit using a transmission line.
2. Description of the Related Art
Conventionally, and as used herein, the term “impulse” refers to any short-duration voltage, current, or wave signal that is used to generate a large amplitude. A periodic impulse signal is referred to as a pulse. However, the term “pulse” is a generic term that includes an impulse and a pulse.
Such a pulse includes a clock pulse and a frame pulse, and is used in a bit synchronization system and a frame synchronization system. More specifically, pulses are widely used in a multiplexing transmission system, a switching system, and a very high-speed communication and positioning system. Each of the above-mentioned systems include an impulse generation circuit for generating a pulse or impulse.
The existing impulse generation circuits can be based on the instant reverse conduction characteristics of a diode, or based on an RC differentiator circuit configured by a resistor R and a capacitor C, etc.
FIG. 1 is a circuit diagram illustrating an example of a conventional impulse generation circuit based on the reverse conduction characteristics of the diode.
Referring to FIG. 1, an input voltage Vin from a power supply is supplied to a capacitor C1. After the voltage Vin is gradually boosted, it drops when a predetermined time has elapsed. The voltage Vin is supplied to a diode SRD through the capacitor C1. The diode used herein is a step recovery diode (SRD). The diode SRD generates an impulse with a predetermined pulse width when the reverse conduction is instantly made at an arbitrary point by the gradual boosting of the voltage Vin. The pulse width depends upon characteristics of the diode SRD used. The diode SRD is sensitive to a temperature variation. The impulse with the predetermined pulse width generated by the instant reverse conduction of the diode SRD is produced as an output Vout.
FIG. 2 is a circuit diagram illustrating an example of a conventional impulse generation circuit based on the RC differentiator circuit.
Referring to FIG. 2, an input signal with a predetermined period and pulse width is amplified to a desired level through an amplifier. The amplified signal is input into the differentiator circuit configured by a capacitor C and a resistor R. The differentiator circuit generates an output signal that is proportional to a rate at which the input signal is changed over time. The output signal is an impulse signal. The impulse signal generated by the differentiator circuit is amplified to a desired level, such that the final output signal Vout is generated. The impulse width depends upon values of the resistor R and the capacitor C that comprise the differentiator circuit. However, the impulse generation circuit using the RC differentiator circuit has irregular characteristics due to input/output impedance dispersion of a used active device as well as dispersion of values of the resistor R and the capacitor C. Fine adjustment of the characteristics is relatively difficult.
FIG. 3 is a circuit diagram illustrating a conventional impulse generation circuit that can adjust a pulse width using a delay time according to the length of a transmission line.
Referring to FIG. 3, an input pulse Vin is inverted, and the inverted pulse is one input of an OR gate 320 serving as a first logic element. A delay line 310 delays the input pulse Vin for a predetermined delay time, and the delayed pulse is the other input of the OR gate 320. The OR gate 320 performs an OR operation on the two inputs to generate an output pulse with a predetermined width. The delay time depends upon the length of the delay line 310. The pulse width depending upon the delay time is adjusted by the length of the delay line 310. The pulse output from the OR gate 320 is one input of a NOR gate 330 serving as a second logic element. The NOR gate 330 receives data at its second input. The NOR gate 330 performs a NOR operation on the pulse and data inputs, thereby outputting one desired pulse. An exclusive NOR gate 340 serving as a third logic element performs an exclusive NOR operation on a signal input obtained by inverting the pulse output from the OR gate 320 and the data input, thereby outputting the other desired pulse. The pulses output from the NOR gate 330 and the exclusive NOR gate 340 are combined, such that the final output signal Vout is output. As described above, the impulse generation circuit with the structure of FIG. 3 can produce a desired pulse width by adjusting the length of the delay line 310. However, because the adjustment of the delay line length is not easy, it is difficult for the pulse width to be finely adjusted.